Activate flow with QR code from internet

Hello! I have a disco ball connected to smart switches/lights, and I want people on the street to be able to turn it on by visiting a website through a QR code.

I tried using ikea buttons but they keep getting stolen!

Basically I need a public facing website that doesn't require login, that will activate a flow in nodered and then forward to another URL (e.g. spotify, youtube etc)

My ISP charges for static IP addresses, so I'd rather not set up a web server on my network unless I absolutely have to!

Thanks so much for your help - really appreciated.